Tests of male hormone levels in women's blood cannot predict diminished sexual function and should not be used in deciding on a course of treatment, Australian researchers report today.
The report in the Journal of the American Medical Assn. questions the assumption among sex researchers that low sexual desire in women has roots in low levels of testosterone or certain related hormones.
This belief has contributed to growing use of testosterone supplements, including a patch worn on the skin, and the frequent use of tests to determine hormone levels.
The study found that the majority of women with low hormone levels did not have low levels of sexual function.
"If a woman with low libido walks into her doctor's office and asks for a blood test to see if she can use that new testosterone patch, well, there's no basis for that," said lead author Dr. Susan Davis of Monash Medical School in Victoria, Australia. "They're totally uninformative."
Dr. Richard J. Paulson, chief of reproductive endocrinology at USC's Keck School of Medicine, who was not involved in the study, added: "You can not oversimplify the problem to simple hormone measurements."
Paulson said the current study, coupled with findings from other research, suggested that the key was not a woman's testosterone level, but rather how much those levels may have changed over time.
The use of a testosterone patch to increase hormone levels might be beneficial, he said, but the study did not address that issue.
Studies have estimated that more than 40% of women experience sexual dysfunction, with the primary effect being low libido. The prevalence of female sexual dysfunction appears to increase with age, beginning in the 30s. Menopause and some surgical procedures, such as removal of the ovaries, can also reduce sexual function.
Davis said decreased sexual desire with age was normal. "But now when most people are living until they're 80, and women are having babies when they're 35, women are saying, 'If I'm going to keep having sex, I need to do something about it,' " she said.
Some studies have shown improvement of sexual function and psychological well being upon receiving testosterone therapies. Procter & Gamble is developing the testosterone patch Invisira to increase female libido.
Davis and her colleagues wanted to find out if women with low sexual function shared a common profile of blood hormones.
The study looked at more than 1,000 women, from 18 to 75 years old, who provided detailed descriptions of satisfaction with their sex lives. Portions of the survey focused on desire, arousal, orgasm, pleasure and self-image. The researchers categorized women who scored in the survey's lowest portions as "low functioning."
The survey results were compared to hormone levels measured from blood samples.
Davis and her team found no relationship between low testosterone levels and low sexual function.
But they did find that women with low sexual function often had low levels of the hormone dehydroepiandrosterone sulfate, or DHEAS, a precursor compound that is converted by cells into testosterone and estrogen.
There were too many women, however, with normal sexual function who also had low DHEAS levels to use the measurement as a diagnostic tool.
Dr. Glenn D. Braunstein, chairman of the department of medicine at Cedars-Sinai Medical Center, said the best diagnostic tool was still talking.
"Don't waste your time measuring testosterone or DHEA. It's not gonna help you," he said. "Listen to the patient."